This invention relates to the recovery of metal in aqueous solutions, and more particularly to an electrolytic device for recovering metal in an aqueous bath that is generating metal ions. The metal recovery process proceeds simultaneously with the process that generates the metal ions. The device of the invention is particularly useful in connection with the recovery of silver from fixing solutions used in photographic or X-ray film processing wherein the device is operable to recover silver simultaneously with the fixing process that produces silver ions.
Methods for the electrolytic recovery of metal generally involve the immersion of a pair of electrodes within the aqueous electrolytic solution containing metal ions. A voltage of sufficient magnitude is impressed across the electrodes to effect migration of the metal ions to the cathode surface, whereupon the metal ions become deionized and deposit a continuous film or coherent plate on the cathode surface. Thereafter the metal plate can be removed.
For example U.S. Pat. No. 3,953,313 discloses an electrolytic cell containing a plurality of alternate anode and cathode plates spaced laterally and having a sheet of mesh material on each electrode thus providing a plurality of holes therein. Alternatively, each electrolytic cell has a housing provided with an inlet pipe and an outlet pipe adapted to transfer the electrolytic solution from a storage container to the electrolytic cell. The electrolytic solution is processed in the electrolytic cell.
Other methods of metal recovery are shown in U.S. Pat. Nos. 3,663,416 and 4,174,026 wherein a helical or spiral electrode element is placed in a container wherein fluid passageways interconnect the container with a storage or metal ion producing bath. The prior art processes, however, require separate self-contained electrolytic cells to recover the metal in a separate process from that which produces the metal ions.
The device of the present invention, however, is effective to recover metal from an aqueous bath that generates metal ions simultaneously and in the same unit in which the metal ion generating process is proceeding. As indicated above, the device is particularly useful for recovering silver from the fixing bath utilized in a photographic or X-ray fixing process that results in the generation of silver ions.